- Metformin, a diabetes drug, may reduce long Covid risk by 40-50% when started early
- The COVID-OUT and ACTIV-6 trials showed consistent benefits of early metformin use
- Metformin is generally safe but not suitable for those with severe kidney or liver issues
Long Covid, a prolonged, often painful syndrome following acute SARS-CoV-2 infection, has affected millions globally, leaving survivors grappling with persistent fatigue, cognitive challenges ("brain fog"), breathing difficulties and more, long after initial recovery. Estimates suggest that up to one in ten people who contract Covid -19 may develop lingering symptoms lasting months or even years, profoundly impacting quality of life and healthcare systems alike. While vaccines and antivirals like Paxlovid help prevent severe acute outcomes, they do not fully eliminate the risk of long Covid. This has driven researchers to explore additional preventive strategies, including repurposing commonly prescribed medications. One such drug, metformin, a cornerstone of type 2 diabetes treatment for decades, has emerged as a promising candidate.
Recent large clinical trials and real-world data now indicate that metformin, started during the early phase of Covid -19 infection, can cut the risk of clinician-diagnosed long Covid by around 40-50% compared with placebo. Researchers caution, however, that this finding reflects prevention rather than treatment of established long Covid, and timing appears critical for benefit.
What Is Long Covid?
Long Covid, also known as post- Covid -19 condition or PASC, refers to symptoms persisting weeks or months after acute infection that cannot be otherwise explained. Common manifestations include chronic fatigue, muscle pain, cognitive impairment, persistent respiratory issues and autonomic dysfunction.
The exact mechanisms underlying long Covid are still being studied, but experts believe it involves immune dysregulation, ongoing inflammation, viral persistence and other complex biological processes.
How Metformin Could Help Prevent Long Covid
Metformin has been prescribed since the 1950s to manage high blood sugar in people with type 2 diabetes. Its long track record, safety profile, low cost and global availability make it attractive for repurposing in other conditions. Laboratory studies have also shown metformin may influence immune response and viral replication, offering a biological rationale for its potential role in Covid -related conditions.
The Evidence: Clinical Trials and Real-World Data
1. COVID-OUT Trial
The landmark COVID-OUT trial, published in The Lancet Infectious Diseases, randomized adults with acute Covid-19 to receive metformin or placebo within days of symptom onset. Results showed that people taking metformin had a 41% lower risk of developing long Covid over a 10-month follow-up period. Importantly, starting metformin earlier (within three days) was associated with up to a 63% reduction in long Covid rates.
Worldwide re-analyses and observational data align with this finding, suggesting that early metformin use may shorten viral load duration and modulate immune responses that otherwise contribute to persistent symptoms.
2. ACTIV-6 Trial
A second major study, the ACTIV-6 trial, assessed metformin in a broader population, including people with normal BMI and prior immunity. At six months, metformin recipients had approximately 50% lower rates of clinician-diagnosed long Covid compared to placebo, reinforcing consistency across diverse groups.
Magnitude of Effect
Across multiple studies, randomized trials and analyses of electronic health records, the risk reduction associated with early metformin treatment ranged from roughly 40% to 60%, a substantial finding given the global burden of post- Covid conditions.
Safety, Limitations and Clinical Advice
Metformin is generally well-tolerated, though it can cause gastrointestinal issues (e.g., nausea, abdominal discomfort) in some people. Unlike many diabetes medications, metformin alone rarely causes dangerously low blood sugar. However, it is not suitable for everyone. People with significantly reduced kidney function, severe liver disease or certain metabolic conditions may face higher risks of rare complications like lactic acidosis.
Importantly, current evidence supports metformin for long Covid prevention when started early in infection, not as a treatment for established long Covid symptoms. The benefits diminish if the drug is started weeks or months after acute illness, and research in children is limited.
Experts stress that individuals should not self-medicate and should discuss options with healthcare professionals, who can tailor recommendations based on medical history and risk factors. Emerging research paints a cautiously optimistic picture: A familiar, inexpensive diabetes drug, metformin, may significantly reduce the likelihood of developing long Covid when taken early in the course of SARS-CoV-2 infection.
While not a cure-all, this strategy could become a valuable component of Covid -19 care, especially for high-risk adults. As scientists continue to explore underlying mechanisms and refine treatment protocols, the key take-home message remains clear: Timely intervention matters, and repurposed medicines may play a role in reducing the long-term toll of Covid-19.
Disclaimer: This content including advice provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your own doctor for more information. NDTV does not claim responsibility for this information.
